1. Field of the Invention
The subject invention relates to metal casting and pouring technology and, more specifically, to screening a stream of molten metal.
2. Information Disclosure Statement
A screening apparatus for molten metal is known from German Patent No. DE 28 34 746, which discloses bellows provided with ring flanges on both sides for connection on one side to the bottom of a pouring vessel and on the other side to the upper side of a casting mold.
In order to render the pouring spout, and if necessary the casting interval space, accessible, the lower ring flange can be lifted rapidly to the upper ring flange by folding the bellows by means of a lifting device.
A protective gas is introduced into the area surrounding the pouring stream via a gas distribution ring that is connected to a supply line leading to the outside. However, maintenance of a protective gaseous atmosphere in the area surrounding the pouring stream is often impeded by the fact that the bellows starts to leak relatively quickly. If this leakage occurs during the casting process, an attempt to prevent the entrance of air to the pouring stream must be made by means of an increased supply of protective gas in an effort to avoid reoxidation. Otherwise the pouring process must be interupted, which is very undesirable. In addition to the expenses for large amounts of protective gas, the corresponding frequent replacement of bellows adds to operating expenses.
The above mentioned German Patent No. DE 28 34 746 also cites many patent references in turn.